1. Technical Field
The present application relates generally to a method for transmitting short messages in a mobile communication system and, in particular, to a method for simultaneously transmitting a short message to a plurality of called subscribers in a GSM (Global System for Mobile Communication) system.
2. Description of the Related Art
A GSM system is a European cellular mobile telephone system in which traffic and signaling information is transmitted as a digital signal in TDMA (Time Division Multiple Access) format. In general, the signaling and traffic information transmitted between a base transceiver station and a GSM terminal has a burst form of 156.25 bits. Particularly, the data burst of the traffic channel includes 3 start bits, 58 message bits, 26 trailing sequence bits, 58 new message bits, and 3 stop bits. In addition, a guard space exists between successive bursts to distinguish between them, making the total length of a burst equal to 156.26 bits (with a burst time of 0.577 ms). Data bursts of other channels have 8 respective frames which are sequentially positioned on a radio channel frequency. These data bursts include compressed digital traffic information, voice information and character information.
Referring now to FIG. 1, a block diagram illustrates a GSM system in which the present method for transmitting short messages can be implemented. A home location register (HLR) 160 contains data for each of a plurality of mobile subscribers such as a home location of each subscriber and an address of a service center in which a short message for a GSM terminal is stored. The address of the service center is deleted after the short message is transmitted. A visitor location register (VLR) 150 includes data such as an actual or latest known location of a subscriber, an ON/OFF state of a GSM terminal and a secret number. A mobile switching center (MSC) 100 is connected to another MSC 200, a public switched telephone network (PSTN), an integrated services digital network (ISDN), and a short message service center 180. A first base station subsystem (BSS) 110 includes a base station controller (BSC) 112 and a plurality of base transceiver stations (BTSs) 114 and 116. A second base station subsystem (BSS) 120 includes a base station controller (BSC) 122 and a plurality of base transceiver stations (BTSs) 124 and 126. The BSCs 112 and 122 are connected to the MSC 100 and to at least one BTS (e.g., one of the BTSs 114, 116, 124, and 126). In addition, the BTSs 114 and 124 control the transmission of a message between a corresponding one of GSM terminals 10, 20, 30 and 40 and the MSC 100, and forms a radio link to transmit voice and data signals.
A subscriber authenticator 140, operatively coupled to the MSC 100, confirms an authentication number (or “secret number”) of a subscriber in order to prevent other mobile subscribers from fraudulently using the identification of another subscriber. The short message service center 180 stores data such as short messages and (as explained in further detail below) a group identifier and a plurality of addresses associated with the group identifier. The telephone numbers of called subscribers are stored in these addresses. If a short message cannot be transmitted to the called subscriber number (i.e., the terminal of the called subscriber is busy or the called subscriber does not answer a call), the short message service center 180 repeatedly attempts to transmit the short message by a preset number of times. Short message service gateways 170 and 190 connect MSCs 100 and 200, respectively, to the short message service center 180.
Referring now to FIG. 2, a block diagram illustrates a GSM terminal (e.g., the GSM terminal 10 of FIG. 1) in which the present method for transmitting a short message can be implemented. A controller 1 controls the overall operation of the GSM terminal. For example, the controller 1 causes the GSM terminal to generate short message group registration information for transmitting a short message during a “short message group transmission mode” (as explained in further detail below). A memory 2 stores various programs that are used by the controller 1 for performing short message group transmission and stores data generated during the execution of these programs. A key entry unit 3 has a plurality of numeric keys and function keys and generates key data. A display unit 4 displays the key data generated from the key entry unit 3, and displays the operating status of the GSM terminal. An audio circuit 6 converts an audio signal received through a microphone MIC, as well as data received from the controller 1, into an intermediate frequency signal. Further, the audio circuit 6 processes an intermediate frequency signal received from an RF circuit 5, and supplies processed data to the controller 1 and a processed audio signal to a speaker SP. The radio frequency (RF) circuit 5 demodulates an RF signal received through an antenna AT into an intermediate frequency signal. Moreover, the RF circuit 5 modulates an intermediate frequency signal received from the audio circuit 6 into an RF signal and transmits the RF signal through the antenna AT.
A conventional short message transmission operation will now be discussed with reference to FIGS. 1 and 2. If a menu key on the key entry unit 3 of the GSM terminal (e.g., GSM terminal 10) is selected, the controller 1 causes the display unit 4 to display a plurality of menus. If a short message service menu is selected among the displayed menus, the controller 1 instructs the calling subscriber to sequentially input a short message service center number, a short message, and a destination address (i.e., a called subscriber). Conventionally, only one destination address can be input. Once the short message service center number, short message and destination address are input, the controller 1 determines if a transmit key (from the key entry unit 3) is selected. If the transmit key is selected, the controller 1 transmits the short message information (i.e., the service center number, the short message and the destination address) through the RF circuit 5 in the prescribed data burst format.
Referring again to FIG. 1, the BTS 114, for example, receives the short message information transmitted from the GSM terminal 10 and then transmits the information to the BSC 112. The BSC 112 then transmits the short message information to the MSC 100. The MSC 100 detects the called subscriber number included in the short message information and determines if the called subscriber number is a registered subscriber number. If the called number is a registered subscriber number, the MSC 100 will detect the service center number (i.e., the service center address) from the short message information and the MSC 100 is then switched to the short message service center 180. The service center address is temporarily stored in the HLR 160. The short message information is matched through the short message service gateway 170 and transmitted to the short message service center 180. The short message service center 180 stores the short message information and detects the destination address. The short message service center 180 then transmits the short message to the destination address via the MSC 100. If the destination address is the GSM terminal 40, for example, the short message service center 180 will transmit the short message to the GSM terminal 40. If the GSM terminal 40 is busy or the call is not answered, the short message service center 180 repeatedly attempts to transmit the short message by a preset number of times.
As demonstrated above, the short message is transmitted to a particular destination terminal by point-to-point links. Moreover, when the calling subscriber wants to transmit a short message to a plurality of terminals using the conventional method discussed above, the short message must be transmitted to each of the terminals one by one (i.e., only one destination address can be designated via the GSM terminal for each set of short message information transmitted to, and processed by, the corresponding MSC).